Bounce "550 5.7.1 ... blocked using Spamhaus": what to do
What's happening: The receiving server looked up the sending IP or your domain on a Spamhaus blocklist and found it listed. If you use Google Workspace, Microsoft 365 or another hosted provider, the listed IP is usually theirs, not yours, so read the bounce closely to see exactly what was listed.
How to fix it
- Copy the IP or domain from the bounce and look it up at check.spamhaus.org. The result says which list and why.
- If it's your own server or your domain, fix the cause first: a compromised mailbox or website sending spam, a bought or scraped list, or an open relay. Delisting before fixing just gets you relisted.
- Then request removal through the link Spamhaus shows for that listing.
- If it's your hosted provider's shared IP, contact their support; you can't delist their IPs yourself.
Not sure which record is wrong? Check your domain free: it shows which of SPF, DKIM and DMARC is failing, in 5 seconds, no signup.